You’ve hiked five miles to an alpine lake, limbered up your rod and wet the line. . . only to reel in a scrawny fish with a big head. You realize with dismay the scenic backcountry lake is full of stunted brookies. Ugh.
Over the decades authorities have tried various strategies to remedy such unhappy situations, but none have worked out. It’s hard to eliminate unwanted over-reproducing fish populations.
Now a new approach is being tried at Little Gee Lake, a shallow, drive-to lake in Skagit County northwest of Darrington at 4200 feet of elevation. Washington Dept. of Fish and Wildlife (WDFW) aims to extirpate overpopulating Eastern Brook Trout using special hatchery “YY male” fish. If the pilot project is successful, in a few years there will only be male fish in the lake, leading to complete fish eradication and the chance to introduce non-reproducing trout and establish a quality fishery.
The approach with YY male fish uses “a traditional hatchery technology in a nontraditional way,” according to Idaho Fish and Game, which pioneered the method around ten years ago in streams. Field trials in Idaho are still underway to determine efficacy and add refinement.
Theoretically the approach should work at Little Gee, says Justin Spinelli, the WDFW biologist who is managing the Little Gee project, which he says will be a minimum 10-year effort. He hopes that success will provide proof of concept for other lakes in Washington, and for lakes in other states as well. Spinelli emphasizes that fish and lake environments are complicated and favorable results do not always follow from theory. There are a number of uncertainties, and sustaining the effort can be challenging.
The strategy depends on introducing male fish that have YY sex chromosomes instead of the usual XY chromosomes (as humans have as well). The YY males are sometimes called supermales. When YY supermales mate with a female, which have XX sex chromosomes, only male offspring (XY) can be produced. It takes multiple years of annual stocking with YY fish until a water body has only male fish and so no future offspring. Once a lake is devoid of unwanted fish, non-reproducing fish that grow to respectable size can be introduced.
This is how quality fishing could be established in high lakes currently teeming with stunted fish.
Eastern Brook Trout, aka EBs or brookies, non-native to western North America, are the fish typically overpopulating lakes. You can land a nine-year-old fish that is only five-inches long. Stunted, starving fish can be scary to behold and their ravenous ways are bad for the water body’s overall biological health. Approximately 200 lakes in the high country of Washington are afflicted with over-reproducing trout. That number is known thanks to efforts by the Hi-Lakers and Trailblazers who provide lake surveys to WDFW.
“Overpopulated lakes are my pet peeve,” says Rex Johnson, a longtime Hi-Laker and Trailblazer who retired from the Dept of Oceanography at the UW as senior research engineer in 2008. “I’m bummed if I go to a lake and it’s full of stunted fish. And it’s an ecological disaster.”
Restoring overpopulated mountain lakes has become Johnson’s mission. He spent 17 years supporting a rehabilitation experiment at Anderson Lakes in Lewis Country, with Tiger Muskies the voracious apex predator fish introduced to eliminate stunted fish. He supported a similar effort at Forest and Lonesome lakes in Pierce County using Tiger Trout. Neither of those were successful, says Johnson.
Spinelli calls Johnson “the catalyst” and “impetus” for WDFW’s Little Gee project.
One critical requirement for success at Little Gee is removing a large proportion of the existing brookies by gillnetting, so the YY males, introduced as small fry, have a chance to get established. “We have to suppress the existing populations by at least 75-percent before starting the introduction of YY males” says Spinelli.
The timeline for the Little Gee project is roughly 2 to 4 years of suppression (gillnet removal of fish), and 5 to 6 years of introducing YY males. The public will be allowed to visit and fish at Little Gee during this time period, and the fish are safe to handle and eat, both Spinelli and Johnson say.
The gillnetting effort this year will take place August 19 to 22nd with help from Trailblazer and Hi-laker volunteers. They will remove the fish from the nets (not easy and labor intensive), measure, weigh, and sex them, and record the information. This is the second year of gillnetting. Although Little Gee is a drive-to lake, the team is using lightweight backcountry gillnets, just under 2-pounds apiece. The idea is to treat the lake as if it were a typical mountain lake that required a hike to reach. About five gillnets will be set per night. The backcountry gillnets are effective only for fish 5-inches or larger, one reason suppression has to take place over multiple years.
“I helped pull the gill net,” says Jon Jones, a cancer biologist who assisted last year when he was Hi-Laker president. “It was fun, [but] difficult. The fish were really entangled and it was hot, there were yellow jackets. . .[but] we felt like we were doing something that mattered, and using modern science. I’m really behind the project.”
At some point, almost assuredly not after this year’s gill netting, the YY male fish will be introduced. They will come from hatcheries in Idaho that use female hormones to force males to produce eggs, a process which requires FDA approval. The cost is relatively low but there is limited supply and competition among various projects. “The YY fish are difficult to come by,” says Johnson. Even after the YY fish are introduced, the brookies will have to continue to be suppressed, says Spinelli, and how that will be accomplished is still uncertain.
Here’s how Idaho Fish and Game describes the multi-step process of creating the YY male fish:
<<The YY technique begins in a hatchery, where young brook trout are exposed to low-doses of a naturally occurring female hormone, estradiol, which has no effect on female fish, but causes male fish to produce eggs when they mature. The egg-producing males are crossed with standard males, which produce about 25 percent YY-male offspring. Those offspring are used to produce another generation that will theoretically produce exclusively male offspring when bred with any other brook trout.
Brook trout produced in the program for stocking in the wild are not exposed to any hormones and appear like all other brook trout, but they carry two male chromosomes instead of one.
While it sounds complex, it’s a fairly simple method of using hormones to affect gender in a segment of the population, then selectively breeding them to get an entire population to produce one gender. It’s routinely done in commercial aquaculture hatcheries to raise identical-looking food-fish, increase growth rates, and control reproduction.
If the program with brook trout proves successful, the “YY male” method could eradicate or limit other undesirable fish species in select waters, perhaps even large bodies of water with carp infestations, or other unwanted fish that limit game fish populations and harm habitat.>>
[https://idfg.idaho.gov/press/fish-and-game-develops-new-way-control-fish-populations 2016. For a technical paper see https://collaboration.idfg.idaho.gov/FisheriesTechnicalReports/Production and Evaluation of YY-Male Brook Trout to Eradicate Nonnative Wild Brook Trout Populations 2.pdf]
Spinelli hopes that this pilot project will prove the method practical and cost effective for lakes in Washington state. To that end he has designed the field-aspect of the project to conform to what would be a reasonable effort for restoring a remote lake, which he says is roughly one to two weeks of special project work per year by local fish managers who are limited in staff and time.
Currently the YY male approach is also being deployed in the Sullivan Creek system in eastern Washington to remove Brook Trout, a partnership between the WDFW and the Confederated Tribes of the Colville Reservation.
Solutions for the stunted-fish problem in lakes tend to be problematic. Fishing the lake out by gill netting, for example, is labor intensive and hence expensive, and only works in lakes with a simple structure. Removing catch limits so people can keep all they want shows no long-term difference. Introducing apex predators who feed on the small fish mostly just grows large apex predators.
Using a chemical like rotenone, a poison for fish now classified as a pesticide, can be effective, but can cost $5-10,000 per lake or substantially more, and lakes have to be smallish and generally with easy access, i.e., be drive-to; plus there is often vocal resistance to using toxicants which can kill other organisms besides fish. Few mountain lakes are drive-to, and if helicopters or other transportation or equipment is required the price escalates quickly to prohibitive.
“Eastern brookies are a tough nut to crack,” Johnson says. “They can reproduce in a cup of water.” But he has high hopes for Little Gee and YY supermale fish as a workable, economical solution for rehabilitating lakes overpopulated with Brook Trout. “Little Gee Lake will be the first test of this concept here in Washington in a mountain lake,” he says. “This is an extremely important experiment.”
If you would like to help on the project, contact Johnson at:
rexvjohnson2 at gmail.com
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